1. Field of the Invention
The present invention relates to an occupant protection apparatus which deploys an air bag at a timing according to the seated posture of an occupant, thereby to protect the occupant at the time of collision of a vehicle.
2. Description of the Related Art
Such a kind of conventional occupant protection apparatus is disclosed in Japanese Patent Kokai (Unexamined Laid-Open) No. Hei. 5-1324. The arrangement of this conventional occupant protection apparatus will be explained with reference to FIG. 8.
In this arrangement, acceleration of a vehicle generated by the collision of the vehicle is detected by an acceleration sensor 1, then an acceleration signal from the acceleration sensor 1 is integrated twice by first and second integration circuits 2 and 3 to obtain an amount of deviation, and further the acceleration signal is applied to a first coefficient circuit 4 through the first integration circuit 2 thereby to obtain a speed of the vehicle. The acceleration signal from the acceleration sensor 1 is applied to a second coefficient circuit 5 to obtain the acceleration multiplied by a coefficient. These deviation amount, speed and the coefficient-multiplied acceleration thus obtained are added by an adding circuit 6 to estimate a deviation amount after a predetermined time period. When the estimated deviation amount reaches a predetermined position, an ignition signal is supplied to a detonator 7 through the adding circuit 6 thereby to inflate an air bag.
Since the seated posture, sliding amount of a seat or the like are determined in a limited range to some extent for each driver, there is not a large difference in the distance for the respective drivers from the surface of the air bag inflated at the maximum to the initial position of the head of each driver. Thus, as for drivers, aforesaid method of inflating the air bag based on the estimated deviation amount of the head of an occupant can be realized.
However, an occupant sitting on the seat next to a driver may cross his or her legs or lie on the seat by reclining the seat at a large inclined angle with his or her preference, so that the initial position of the head portion of the occupant at the seat next to the driver differs greatly. Thus, there is a problem that the aforesaid estimation method can not be employed for an occupant sitting on the seat next to the driver.
Accordingly, the present invention has been performed so as to obviate the aforesaid problem of the conventional art.
An object of the present invention is to provide an occupant protection apparatus and method which measures at every lapse of a predetermined time period the position of the head of an occupant from an instrument panel, for example, of a vehicle, then estimates the position of the head after a predetermined time period based on the measured position, and provides an ignition signal to a detonator at a suitable timing based on the estimated position thereby to inflate an air bag.
Another object of the present invention is to provide an occupant protection apparatus and method which measures at every lapse of a predetermined time period the position of the head of an occupant from an instrument panel, and the measured position is interpolated by a deviation value which is obtained by integrating twice a magnitude of acceleration of a vehicle, thereby to measure the position of the head of the occupant from the instrument panel with a high accuracy.
According to a first aspect of the present invention, there is provided an occupant protection apparatus comprising:
an acceleration sensor which detects acceleration of a vehicle at a time of collision and outputs an acceleration signal representing a magnitude of the acceleration;
a timing control circuit which measures a distance between the head of an occupant sitting on a seat slidable along a longitudinal direction of the vehicle and having a reclining function and an instrument panel, compares the distance thus measured with threshold values and controls a timing for igniting a detonator for driving a main body of the protection apparatus in accordance with a result of the comparison; and
an ignition control circuit which ignites the detonator in accordance with the timing thus controlled when the acceleration signal is outputted from the acceleration sensor, wherein
the timing control circuit sets the threshold values to be compared with the distance between the head of the occupant and the instrument panel in correspondence with an inflation suppression area, an inflation area without timing delay and an inflation area with timing delay, respectively.
According to a second aspect of the present invention, there is provided an occupant protection apparatus, comprising a plurality of detonators are provided for a single inflator.
According to a third aspect of the present invention, there is provided an occupant protection apparatus, wherein the threshold values set by the timing control circuit are set in accordance with the distance from the instrument panel in an order of the inflation suppression area, the inflation area without timing delay and the inflation area with timing delay.
According to a fourth aspect of the present invention, there is provided an occupant protection apparatus, wherein the timing control circuit, when determines that the head of the occupant locates in the inflation area with timing delay, estimates a timing at which the head of the occupant shifts to the inflation area without timing delay from the inflation area with timing delay, and simultaneously ignites a plurality of the detonators at the estimated timing.
According to a fifth aspect of the present invention, there is provided an occupant protection apparatus, wherein the timing control circuit, when the timing control circuit determines that the head of the occupant locates in the inflation suppression area, the timing control circuit ignites one of the plurality of detonators.
According to a sixth aspect of the present invention, there is provided a method comprising the steps of:
measuring repeatedly with a first period of time a distance between the head of an occupant sitting on a seat and an instrument panel by using output signals of a plurality of sensors;
integrating twice with a second period of time shorter than the first period of time an acceleration signal representing a magnitude of acceleration of a vehicle from an acceleration sensor which is one of the plurality of sensors thereby to obtain an amount of deviation of a position of the head of the occupant; and
subtracting the amount of the deviation thus obtained
through the integration from the distance thus measured with the first period of time thereby to estimate a distance between the head of the occupant sitting on the seat and the instrument panel.
According to a seventh aspect of the present invention, there is provided an occupant protection apparatus comprising:
a first distance measuring means which measures repeatedly with a first period of time a distance between the head of an occupant sitting on a seat and an instrument panel by using output signals of a plurality of sensors;
an integration means which integrates with a second period of time shorter than the first period of time an acceleration signal representing a magnitude of acceleration of a vehicle from an acceleration sensor which is one of the plurality of sensors thereby to obtain an amount of deviation of a position of the head of the occupant;
a second distance measuring means which subtracts the
amount of deviation thus obtained by the integration means from the distance thus measured by the first distance measuring means thereby to measure a distance between the head of the occupant sitting on the seat and the instrument panel; and
a driving control means which allows an ignition signal for igniting and driving a detonator to be outputted when the distance measured by the second distance measuring means exceeds a threshold value.
According to an eighth aspect of the present invention, there is provided an occupant protection apparatus, wherein the threshold value includes a first threshold value which is set in a vicinity of the instrument panel and defines an inflation suppression area for restricting inflation of an air bag between the instrument panel and the occupant, and a second threshold value which is set so as to distinguish an inflation area without timing delay set at an outer side of the inflation suppression area from an inflation area with timing delay set at an outer side of the inflation area without timing delay, and wherein
the driving control means subtracts the amount of the deviation calculated by the integration means from the distance measured by the first distance measuring means to obtain a distance between the head of the occupant sitting on the seat and the instrument panel only when it is determined that the head of the occupant sitting on the seat locates in the inflation area with timing delay.
According to a ninth aspect of the present invention, there is provided an occupant protection apparatus, wherein the driving control means allows to supply an ignition signal for driving the detonator when it is determined that the distance between the head of the occupant and the instrument panel thus obtained is shifted into the inflation area without timing delay.